Radio resource management solutions for WCDMA FDD systems with asymmetric UL/DL carrier allocation

This paper concerns frequency division duplex cdma systems (WCDMA FDD, cdma2000, etc.) to which extension frequency bands might be added, e.g. for capacity enhancement reasons. Such asymmetric capacity enhancements might be desirable in the future due to increased data transmission over mobile networks especially when asymmetric data is transmitted like, for example, in mobile Internet browsing. Here it is assumed that the frequencies to be added are in downlink. In such a case the one-to-one coupling of uplink (or reverse link) and downlink (or forward link) frequencies is not valid any more. This paper illustrates a new interference scenario that can occur with the new downlink extension bands, and introduces new RRM (radio resource management) solutions for this interference case. The interference mechanism is illustrated for WCDMA. The assumed frequency scenario is WCDMA/FDD uplink/downlink plus additional FDD downlink, e.g. at 2.5 GHz band identified by ITU-WP8F. The new type of interference can be detected by additional mobile station measurements that benefit in efficiency from co-siting of extension and existing frequencies. Both interference detection and avoidance being based on RRM allows flexible and efficient use of extension bands with little impact on current specifications and products.